1. Field of the Invention
This invention relates to an improvement of a linear guide apparatus comprising a guide rail and a slider movable on it through rolling of balls interposed therebetween.
2. Description of the Prior Art
A linear guide apparatus has been disclosed, for instance, by instance U.S. Pat. No. 4,929,095 which comprises: an axially extending guide rail with ball rolling grooves formed in both corner edges between an upper surface and both side surfaces; a slider mounted on the guide rail and movable in an axial direction and having ball rolling grooves formed in an inner surface at positions respectively opposing the ball rolling groves of the guide rail, and a plurality of balls mounted in the mutually opposing ball rolling grooves of the guide rail and the slider, and the slider including a slider body, end caps secured to both ends of the slider body, and a ball retainer held by the end caps which is made up of a rectangular frame-shaped main portion, and engaging portions protruded axially from opposite ends of the main portion, the engaging portions being engaged with ball retainer locking portions formed in the end caps to secure the ball retainer to the slider body.
In the conventional linear guide apparatus, the ball retainer is positively fixed by engaging the ball retainer locking portions of the end caps with the engaging portions of the ball holder as was described above. Hence, the apparatus suffers from the following problems: Components forming the apparatus are unavoidably fluctuated in dimension when manufactured; therefore, it is unavoidable that the end caps are shifted in position when connected to the slider body, the ball retainer is shifted in position when coupled to the end caps, or the engaging portions of the ball retainer is shifted. Hence, frequently the ball retainer secured to the slider is greatly shifted towards the train of balls rolling in the ball rolling grooves of the slider. If the ball retainer is shifted in this manner, it applies a great pressure to the balls, as a result of which the balls are not smoothly circulated, thus adversely affecting the operation of the apparatus. The end caps and the ball retainer are injection-molded products of synthetic resin. Hence, even if the molds thereof are satisfactory, the resultant product is often unsatisfactory; that is, the ball retainer mounted is shifted in position depending on delicate differences of molding conditions. In this case, such unacceptable products will be formed in great quantities, and it will take a great deal of labor and time to fix them. However, it is not desirable to increase the manufacturing accuracy of the components of the linear guide apparatus, because it will increase the manufacturing cost of the latter.